1. Field of the Invention
The present invention relates to a machine translation system, and in particular, to a method of and an apparatus for automatically and objectively evaluating quality of sentences translated through a machine translation.
2. Description of the Related Art
In a machine translation system between natural languages, for example, between Japanese and English, there has been difficulty in developing a translation quality similar to that developed by a human translator. Consequently, it is important for the developer and the user of the machine translation system to quantitatively and objectively evaluate the quality of sentences resultant from the machine translation.
Conventional technologies relating to evaluation of quality of translated sentences have been described, for example, on pages 1197 to 1202 of the "Journal of the Information Processing of Society of Japan", Vol. 26, No. 10, October 1985 and on pages 207 to 212 of the "Machine Translation" written by J. Lehrberger and L. Bourbeau and published from JHON BENJAMINS PUBLISHING COMPANY in 1988. Typically, according to a conventional method of evaluating translated sentences, for fidelity of translated sentences with respect to original sentences and intelligibility of translated sentences, there have been beforehand determined ranks or grades and criteria for judgement of such ranks so that a human evaluator checks each translated sentence obtained from the machine translation system to thereby determine the rank thereof.
However, in this type of evaluation according to the ranks, the evaluation of quality of translated sentences is accomplished by a human and necessitates quite a long period of time. Moreover, the decision of ranks for translated sentences varies from individual to individual and hence there arises a problem that the quality evaluation cannot be definitely regarded as objective.